Pressure limiting device



Aug. 13, 1940.

l.. A. COLE 2,211,052

PRESSURE LIMITING DEVICE Filed March 22, 1938 2 Sheets-Sheet l l5 'Il 4Zl' '30 '38 a 49 .y L ff G o Z0 l l 19 o 16 d" :Z5

17 257m" l' 1 .ZZ as 57 E ,f l1 l. J

f 4 n l 54 37.

i l f7 gk l Euler/Zur ZameaL/e 55 56 1 TMW 7m fm PRESSURE LIMITINGDEVICE l 2 Sheets-Sheet 2 Filed March 22, 1958 fr I i |||1||I1||1 ,2 VHUIIIINNNIMINIU f l, Ii l Il m n OU O O O ullllllmr'l Patented Aug. 13,1940 UNirs stares iPTENT OFFIQ PRESSURE LMITHNG DEVICE tario, CanadaApplication March 22,

3 Claims.

This invention relates to a pressure limiting or pressure controldevice. .Throughout the various industries, pressure systems andpressure devices are employed, operated hydraulically and pneumatically,and in many cases there is danger of the creation` of excess pressure,and likewise pressure drops which are disadvantageous, particularlyexcess pressures where as a result, breakage of machine parts andimproper operation of the machinery may result.

The present invention is designed to obviate disadvantages of thischaracter by providing a simplified form of pressure limiting or controldevice which will give a warning signal when the pressure tends to riseabove or drop below a given range and may also function to prevent theapplication of excess pressure and prevent a drop in pressure below aygiven point.

The invention will be fully apparent through the following speciiicationand accompanying drawings, the novel pressure limiting apparatus beingydescribed by way of example as applied to control hydraulicallyoperated wood pulp grinders and employed as part of the controllingmechanism of a governor for wood pulp grinders.

. ,Referring to the drawings: y

Figure 1 is a front elevation of the pressure limiting apparatus, partlyin section, which is combined with a pressure gauge of the Bourdon type,the front face of the gauge and the associated apparatus being removedto sho-w the working parts of the device.

f Figure 2 is anl enlarged fragmentary sectional View of the workingparts of the apparatus. l

Figure 3 is a section taken on the line 3-3 of Fig. 2. Figure 4 is aside elevation 0i the pressure gauge casing showing the opening throughwhich the working parts connect with the Bourdon tube.

. Figure 5 is a side elevation oi the casing for vconnecting with thepressure gauge casing and `enclosing' the apparatus, illustrating theslots Bourdon tube.

Figure 7 is a plan view of the movable contact arm, the end of the armcarrying the contact being shown partly in section.

Figure 8 is a plan View of one of the connecting links for holding oneof the stationary Contact arms.

1938, serial No. 197,535

Figure 9 is a side elevation of the link sho-wn in Figure 8'.

Figure 10 is ya perspective View of an angle plate used on thestationary contact arms.

Figure llis a perspective view of a channel plate :5 used in the Contactportion of the Contact arms.

Figure 12 is a side elevation of an adjusting bracket used inconjunction with the stationary contact arms, and v Figure 13 is aschematic view of a governor construction for pulp grinders showing theposition of the pressure limiter and its connection with the pilotvalves for controlling the ow of pressure medium.

Referring to the drawings, A indicates the pressure limiting or controldevice generally, which include a gauge casing I il housing a Bourdontube I I designed to operate through the usual link I2 and otherassociated mechanism, the pressure indicating needle I3 of the gauge.The gauge as a whole may be of conventional construction.

According to the preferred form of construction the gauge casing isoriced as at i4 to permit additional parts to project into the interiorof the gauge casing, while an auxiliary casing I5 is secured en theoutside of the gauge casing to enclose the additional parts. In thisinstance a swingable arm I 5 of insulating material is pivoted on thegauge casing as at I'I, the inner end of the arm being slotted as at I8to receive a pin I9 projecting from an operating member 2i) which isdesigned to be rigidly attached to one end of the tubel I I. Theoperating member is shown in detail inFigure 6 and it may include a pairof spaced apart arms 2| and 22 between which the n tube II is disposedand a rigid connection may be made by soldering the arms to the tube.

The opposite end of the swingable arm I6 projects into the auxiliarycasing I5 and is provided with opposed contacts 23 and 24 which project,40 on each side of the arm. These are designed to cooperate withcontacts 25 and 26 disposed in the ends of adjustable arms 21 and 28which have the same pivot point Il as the swingable arm IG and areformed from insulating material. The arms 45 2'! and 28 are pivoted onthe pivot Il by means of metal plates 29 (see Figs. 8 and 9) which aresecured to one side of the arms, while on the oppolsite side aredisposed metal plates 3i), the inner ends of the plates 29 and 30 beingspaced apart the depth of the arms 21 and 28 to provide in effect abifurcated metallic fitting which will straddle the swingable arm I6 atthe pivotal point.

The outer ends of the plates 30 form adjusting `levers for the arms 21and 28 and are bent upon .105

themselves as at 3I and 32 to provide a resilient projection having aflat bearing surface 33 which will engage with slotted plates or thelike 34 disposed'on the interior curved wall of the auxiliary housing I5and positioned below slots 35 and 36 formed in the curved wall of theauxiliary housing. Bolts or screw threaded pins or other means 31 mayproject through the end of the adjusting levers and through the slots 35and 36 respectively in the auxilary housing I5 to beengaged by theknurled nuts or the like 38 which will hold the adjusting levers in aset position, whereas, upon loosening the nuts the adjusting levers maybe moved backward or forward to move the arms 21 and 28 towards or awayfrom the swingable arm I 6 to the extent of the length of the slots 35and 36 in -the auxiliary housing I5. The contacts 23 and 24 and 25 and26 are connected with terminals 39, 40 and 4I respectively, each beingdisposed on the arm carrying the contacts in question and `theseterminals are suitably connected by lead wires` 42, 43 and 44 withterminals 45, 46 andr 41 within the gauge casing, the latter terminalsbeing connected in the elec'- trical system as will be later referredto, to provide for the proper operation of the pressure limiter.

It will be apparent that 'if the swingable arm I6 is swung about itspivot it will move its contacts 23 and 24 towards or away from thecontacts 25 and 26 on the arms 21 and 28, according to the direction inwhich arm I6 is swung and it will also be apparent,l in view of theconnection between the swingable arm IG and the operating member 26carried on the Bourdon tube, that movement of the tube, as a result ofincreased or decreased pressure therein, caused by the pressure systemto which it is attached, will have the result of operating the swingablearm I6 in a manner such as above described. Moreover, b-y reason of thefact that the slot I8 is inclined to the longitudinal axis of the arm I6and longitudinal axis of the operating member 20, the arm lI6 will becaused to swing with accuracy in response to movementof the tube II asthe pin I9 of the operating member 20 will always co-ntact with eitherof the side walls of the slot I8 during the arcuate movement of the tubeII in `one direction or the other.

It will be obvious of course, that if the co-ntact 26 of the arm 28 ispositioned a Selected distance from the contact 24 of the swingable armI 6, the

movement of the arm I6 towards the arm 28 by 'elements in the system toreduce the pressure.

On the other hand, the co-ntact 25 on arm 21 may be set in the same wayand may be used, if desired, to cause a signal to be given when thepressure has dropped below a desired point and/ or cause operation ofcertain elements in the sys'- tem to increase the pressure. In somecases, however, the arm 21 may only be used to effect the requiredadjustment as between the arms I6 and 28, as will' laterl appear.

In order to demonstrate a practical application of the pressure limiter,it has been shown diagrammaticallyfin Figure 13 asapplied to anelectrical governor for wood pulp grinders, which is one eld in which itmay operate advantageously. Referring particularly to Figure 13, Bindicates the governor as a whole, which is provided with an indicatingwattmeter 48 and a governing wattmeter of the Kelvin balance type 49which is connected with the grinders to control their operation inresponse to the load on the motor operating them, as has been referredto in a copending application and of similar character to that disclosedin United States Patent No. 1,719,- 952.

The governor includes a main water valve for supplying hydraulicpressure for operating the pistons in the hydraulic cylinders of thegrinders. This main water valve is opened and closed completely, or tovarying degrees by means of two pilot valves 5l] and 5I, with pipeconnections 52 and. 53 for operating the main valve. The pilot valve 56may be termed an increasing pilot Valve operating to open Ythe mainvalve by supplying sufcient pressure for this purpose and the pilotvalve 5I may beftermed a decreasing pilot valve for closing the mainvalve. These pilot valves are operated by solenoids 54 and 55, theoperation of which is ordinarily effectedvthrough the governingwattmeter of the governor directly in accordance with the loadrequirements of the grinder motor so that by variation in the controlpressure through the pilot valves 5D' and 5I, as they are selected bythe governing wattmeter, the volume of water fed to the pulp grinders isdirectly controlled. However, conditions may arise which will not permitof smooth operation. For instance, if for any reason one or more of thepockets of the grinders stopped grinding-the load on the motor woulddrop and the wattmeter on the governor would signal forv more load.Thus, through the pilot valve 5I] the main water valve would be causedto open wide and place the entire pressure available on the stones allat once. This naturally is undesirable and might cause breakage.However,- the pressure limiter as above described, functions toeliminate such possibility. For example, assume that normal grindingpressure isv pounds to maintain a load of 2,000 kilowatts onthe motorand that 190 pounds pressure is available through the inlet to the mainvalve of the governor. Under such conditions, and in the case where oneor more of the pulp grinder pockets stop grinding, the load might dropto, say, 1000 kilowatts which would result in the main valve beingopened wide, as above referred to and the entire 190 pounds would'beexerted upon the grinder stones. However, if the pressure limiter wasset to say pounds it would be impossible for the maximum load to beapplied to the grinder, and impossible also for more than 175 pounds tobe applied on the stones, because the limiter would function to Open thedecreasing pilot valve and thus oppose and overpower the increasingvalves which is provided with a smaller orifice than the decreasing.

As shown in Figure 13 the terminal 45 for the swingable arm I6 isconnected with the terminal of the swinging contact of the wattmeter bythe line 56. This mechanism through onestationary contact is ordinarilyconnected with the solenoid 55 by the lead 51, whereas the solenoid 55is directly connected with the solenoid 54 by the line 58, and thelatter solenoid in turn connected through the line 59 with the otherstationary contact of the wattmeter so that one or the other of thepilot valves is operated in accordance with load requirements astransmitted through the'balance mechanism. Howeven'the terminal41 of theswngable arm 25 is connected by the lead 68 with solenoid 55 so that inthe event of contact between the contact 24 of ythe swingable arm I Sand contact 26 of arm 28, the solenoid is operated so as to causedecreasing valve 5I to open when a pressure of 1'15 pounds has beenreached in the system. Operation of the solenoid at this point is causedby initially separating arms I8 and 2S only to the extent which willpermit contact when 175 pounds pressure has been reached in the system.At the sam-e time, through a separate circuit, for example tapped in atthe terminals 45 and 41, a warning light or signal light may be employedto advise the operator as to the conditions obtaining. Moreover, if itis desired to increase the pressure in the system when it has droppedbelow a minimum, the contact 46 may be connected with solenoid 54 of theincreasing valve 58 so that it can be brought into operation when theswingable arm I6 causes contact 23 to engage contact 25 of adjustablearm 21.

To set the pressure limiter to operate at the desired maximum pressure,the knurled nut 38 associated with the arm 21 may be loosened so thatthe adjusting lever may be pulled downwardly until the needle of thegauge registers the correct maximum pressure desired. At this point theknurled nut 38 associated with arm 28 may be loosened and the adjustinglever for the latter moved upward until contact is made between contact26 of arm 28 and Contact 24 of swingable arm I6. The knurled nut orother means employed for fastening the adjusting lever of arm 28 is thentightened at this point and the upper adjusting lever is swung to itsupper limit until it is out of the way. Arm 28 may be used as anadjusting means for arm 21 in the same Way.

When using the pressure limiter to operate for the maximum pressureonly, the upper adjusting lever and arm 21 are used merely for settingthe limiter to operate at the desired pressure and these members arethen moved to their extreme upper position out of operation. This istrue for any grinder system or the like using two pressures and whereina minimum pressure setting is not necessary. In the case of singlepressure systems, as used on pocket grinders, the

upper arm 21 and its contact 25, may be used to valve to effect quickeropening movement of the main valve when a heavy volume of water isrequired to retire the pocket. In such a case this pilot valve comesinto action when the pressure falls below a predetermined point which isgoverned by setting the top arm to the required minimum operatingpressure.

The device, may of course, be employed to signal and/or correctabnormaly low pressure conditions alone or abnormally high pressureconditions alone, or both.

While in the disclosure adjusting levers have been shown for effectingthe adjustment of arms 21 and 28, it will be obvious that the armsthemselves might be formed with extensions to project out to the innersurface of the defining walls of the auxiliary casing so that they maybe connected with means projecting through the auxiliary casing such asthe screw threaded pins 31 and nuts 38 through which adjustment may beeffected.

It will be apparent from the foregoing that the pressure limiting means,as described, may

be generally embodied in pressure systems of various kinds tooperate ata given pressure and to control apparatus to avoid pressure peaksandftroughs as well as to signal as to specified pressure variations. Itwill be realized also that the apparatus involved is of relativelysimple construction and rdurable in construction particularly havingregard to the fact that the operation of the pressure limiting orcontrol mechanism is effected directly through the tube II which is ofsturdy construction. Furthermore, as will have been appreciated theswingable and adjustable arms form a unit having the advantageprincipally of adaptability as an accessory. The unit is, therefore,described as such in the appended claims. Moreover, due to the fact thatthe slot formed in the end of the swingable lever I6 is included so asalways to present its said Walls to the pin I9 of the operating member28 which moves in a substantially arcuate path in one direction or theother in response to pressure variations in the system, the swingablearm I6 will respond accurately in accordance with the movement of thegauge needle I3.

As it is apparent that the device operates to correct abnormal pressureconditions in a pressure system and/or functions if desired as a signalto advise as to abnormal conditions, it will be appreciated that thedevice is referred to as a pressure limiting or control device and alsoas a pressure indicator. It is to be understood therefore, that in theappended claims where a pressure indicator is defined, the structureclaimed applies equally to a pressure limiting or control device.

Various modifications may be made in this invention Without departingfrom the spirit thereof or the scope of the claims, and therefore theexact forms shown are to be taken as illustrative only and not in alimiting sense, and it is desired that only such limitations shall beplaced thereon as are disclosed in the prior art or are set forth in theaccompanying claims.

What I claim is:

1. For use with a pressure gauge which includes a movable tube operablein response to pressure variations in a pressure system, a pressureindicating device a portion of which is designed to be projected througha slot in the gauge casing, comprising a unit bodily mountable on thecasing embodying a plurality of arms pivotally mounted from the casingincluding a swingable arm designed for articulated connection with saidtube to swing said arm through an arc on movement of the tube, and anadjustable arm pivotally connected with the swingable arm on the pivotalaxis thereof, means in connection with said unit for positivelyadjusting and retaining said adjustable arm in predetermined relation tothe swingable arm, and contacts on said arms designed to engage when theswingable arm has been moved to a predetermined position by said gaugetube.

2. For use with a pressure gauge which includes a movable tube operablein response to pressure variations in a pressure system, a pressureindicating device a portion of which is designed to be projected througha slot in the gauge casing, comprising a unit bodily mountable on thecasing embodying a plurality of arms pivotally mounted from the casingincluding a swingable arm designed for articulated connection with saidtube to swing said arm through an arc on movement of the tube and anadjustable arm pivotally connected with the swingable armvon the pivotalaxis. thereof, said arms having contacts thereon designed to engage withone another on predetermined movement of the tube, a detachable easingenclosing said arms and mounted on the gauge casing, and means in`connection with the adjustable arm 4extending through said casingforpositively adjusting and retaining it in predetermined relation tothe swingable arm to permit contact only upon predetermined movementofthe gauge tube.

Y 3; A pressure indicating unit as claimed in claim 2 in which there isprovided a second adjustable arm disposed on the opposite side of theSwingable arm and having means in connection 'therewith extendingthrough the detachable casing for positively adjusting and retaining itin predetermined relation to the swingable arm, said swingable arm beingmovable towards one adjustable arm and away from the other on anincrease in pressure in the system and vice versa,

